1. Field of the Invention
This invention relates to well tools and more particularly to devices for releasably anchoring well tools in well conduits.
2. Description of the Prior Art
Generally, gas lift valves and closely related devices of the retrievable type are releasably anchored in position in the receptacles of gas lift wells through use of locking devices known in the industry as gas lift latches. Many such latches have been designed and patented. Some of these latches are of the type which lock or latch automatically upon being inserted in their downhole receptacle. Examples of this last type of latch are found in the following U.S. patents with the exception of U.S. Pat. Nos. 3,208,531 and 4,294,313.
______________________________________ 2,679,903 3,208,531 3,827,493 4,265,306 3,074,487 3,356,389 3,863,961 4,294,313 3,088,521 3,741,601 3,874,447 ______________________________________
U.S. Pat. No. 2,679,903 issued June 1, 1954 to H. E. McGowen, Jr. et al and discloses a latch member pivotally mounted in a housing and spring biased toward locking position. It can be unlocked only by shearing a pin and lifting a core member out of the way to permit the latch to rotate to unlocked position. The rotating latch member is disk-like and is thin, thus unable to withstand great loads.
U.S. Pat. No. 3,074,485 issued Jan. 22, 1963 to Harold E. McGowen, Jr. and discloses a latch having a ring which is spring biased toward its lower concentric, locked position, but can move upwardly and then to an eccentric position to move past a 180-degree locking shoulder under which the ring will assume a concentric locked position. This latch is not for use in receptacles having 360-degree lock shoulders.
U.S. Pat. No. 3,088,521 issued May 7, 1963 to Shelby J. Graves and discloses a latch device having a body with a blind bore in the side thereof in which a spring-loaded lock plunger is disposed. A spring-loaded core, when depressed, will permit the plunger to retract and enter a receptacle. The plunger then springs outwardly to locked position, after which the core is spring-pressed upwardly into locking position. Depressing the core and holding it depressed will permit the latch device to be withdrawn from its receptacle.
U.S. Pat. No. 3,208,531 issued to Jack W. Tamplen on Sept. 28, 1965. This patent discloses a locking device provided with keys which are retracted while the device is being lowered in a well but after it is stopped below a selected one of a plurality of receptacles and lifted therethrough, its running tool shifts an expander sleeve to an intermediate position to cause a spring to press the keys outwardly. Now, when the device is lowered into the receptacle, the keys will engage therein, and the running tool is then used to force the expander sleeve to a position locking the keys against inward movement.
U.S. Pat. No. 3,356,389 issued Dec. 5, 1967 to John V. Fredd and discloses a locking device employing a pair of C-rings on a body. A finger having broad and narrow regions is disposed in the gaps of the rings. Upon inserting the device in the receptacle, the lower ring, due to its drag, is moved upwardly to a narrow region on the finger and is able to contract and move past the lock shoulder. The upper ring, in the same manner, moves up to a broad region of the finger and, because it cannot contract, will stop the device in proper position. When the device is lifted, the lower ring will return to a broad region of the finger where, because it cannot contract, it will lock the device in the receptacle. Shearing a pin and lifting the finger will permit the device to be withdrawn from the receptacle.
U.S. Pat. No. 3,741,601 issued to William Aaron Dudley on June 26, 1973 and discloses a latch having a fixed core, a sleeve slidably mounted thereabout and pinned in its lower position thereon, and a collet surrounds the sleeve and is slidable longitudinally thereon. The collet can move upward upon encountering the receptacle. In its upper position, its fingers can move inwardly into a recess of the sleeve to move past the lock shoulder of the receptacle. Then the collet fingers spring outwardly therebelow. Upward movement of the device in the receptacle will cause the collet to move down to locked position. The latch is released by shearing a pin and lifting the sleeve so that the collet fingers can retract below it.
U.S. Pat. No. 3,827,493 issued to Ben D. Terral on Aug. 6, 1974 and discloses a ring-type latch device almost identical to that disclosed in U.S. Pat. No. 3,074,485, supra, and operates and functions in the same manner.
U.S. Pat. No. 3,863,961 issued to Robert W. Dinning on Feb. 4, 1975 and discloses a latch device having a fixed core, an expander sleeve is slidably mounted on the core and pinned in its lower position. A cage surrounds the sleeve and is movable longitudinally relative thereto. The cage carries locking lugs in windows formed therein and is spring pressed downwardly. The sleeve holds the locking lugs expanded. The cage is movable upwardly to a position wherein the lugs may retract into a recess of the sleeve. Thus, the latch can be inserted into a receptacle where it latches immediately. The latch is released by shearing the pin and lifting the sleeve from behind the lugs.
U.S. Pat. No. 3,874,447 issued to Harold E. McGowen, Jr. on Apr. 1, 1975 and discloses a collet-type latch device which is identical to that disclosed in U.S. Pat. No. 3,741,601, supra, except for the fact that its collet is a closed collet.
U.S. Pat. No. 4,265,306 issued May 5, 1981 to Gregg W. Stout and discloses a latch device which includes a core fixed to a cage having elongated windows with lugs disposed therein, an expander sleeve is disposed between the core and the cage and slidable relative to them, while a spring biases the lugs downward in the cage windows. The sleeve is pinned in its lower position. In this position, it holds the lugs expanded when they are in their lower position. The lugs are movable upwardly in the elongated windows to a level at which they can retract into a recess of the sleeve until they get past the lock shoulder in the receptacle. They immediately afterwards snap into locked position beneath the lock shoulder. Release of the tool is accomplished by shearing the pin and lifting the expander sleeve to permit the lugs to retract therebelow.
U.S. Pat. No. 4,294,313, which issued to Harry E. Schwegman on Oct. 13, 1981, discloses a slightly different type of latch in that this latch does not latch in its receptacle automatically, yet it is similar to the device of the present invention. The Schwegman latch 47, shown attached in the kickover tool of FIG. 12 of U.S. Pat. No. 294,313, comprises a tubular body 49 having windows in which lugs are disposed. A prong or expander 69 is pinned in its upper position allowing the lugs to retract for insertion in the receptacle. A no-go shoulder on the body limits downward movement of the body after which a pin 51 is sheared and the expander is moved down to expand the lugs to locking position. Lifting the expander releases the latch.
The present invention overcomes the problems associated with the prior art devices by providing a locking device for well tools, which is simple, economical, reliable, and can be run in latched condition and snapped into locking engagement in its downhole receptable. It is also able to withstand great axial loads as a result of great pressure differentials acting thereon. The lugs provide adequate bearing area to support such great loads. Installation and removal of the latch device are simple and easily accomplished.